| Summary: | 碩士 === 國立中興大學 === 獸醫學系暨研究所 === 107 === Canine mammary gland tumors (MGTs) are the most common tumors in female dogs. Current diagnosis of MGTs still relies on cytology, histology, and radiography, while cytology has disadvantage of low accuracy in distinguishing malignant MGT from the benign one, histology is time-consuming and could be limited by small tumor size, and radiography bears low sensitivity in detecting early metastatic lesion during follow-up examination after tumor mass resection. Therefore, it is in need of developing new methods to detect canine MGT malignancies. Autoantibodies (AAbs) against tumor-associated antigens (TAAs) have been shown to be serum-accessible and more stable biomarkers than TAAs themselves for detecting human cancer. We previously identified insulin-like growth-factor binding protein-5 (IGFBP5) as an overexpressed protein in malignant canine MGT tissues. In this study, we aimed to access serum IGFBP5 AAbs in MGT dogs by ELISA, in which the E.coli-expressed recombinant canine IGFBP5 was used as an antigen. Serum samples were collected from 110 female MGT dogs, including 25 with benign tumor, 37 with simple carcinoma, 32 with complex carcinoma, and 16 with multiple malignant MGT, and 37 female healthy controls. Multiple regression analysis revealed that simple carcinoma is a factor most significantly affecting the level of serum IGFBP5 AAbs (p = 0.032). Mann-Whitney U test demonstrated that levels of serum IGFBP5 AAbs in dogs with malignant MGTs (n = 85) were elevated compared to those with benign MGTs (p = 0.014). Notably, comparison between serum IGFBP5 AAb levels in dogs with simple carcinoma and those with benign MGTs also shows statistical significance (p = 0.017). Moreover, receiver operating characteristic (ROC) manifested a good efficacy of utilizing serum IGFBP5 AAb levels in discriminating simple carcinoma from benign MGT (AUC = 0.680; sensitivity: 73%; specificity: 68%; p = 0.017). Taken together, this study reveals for the first time the presence of serum IGFBP5 AAbs in MGT dogs and the potential of serum IGFBP5 AAbs in differentiating malignant MGT subtypes from benign MGT.
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